package bluej.debugmgr;

import java.util.List;
import java.util.ArrayList;

import threadchecker.OnThread;
import threadchecker.Tag;




| History objects maintain a history of text strings. This serves as a
| superclass for various histories (see, for example, ClassHistory,
| FreeCallHistory).
|
| @author Michael Kolling
|
@OnThread(Tag.Any)
public class History
{       
protected List<String> history = null;
   
   protected int maxLength;
   
   private boolean blankAtStart;
    
   
   


| Create a empty history limited to a given maximum
| number of entries.
|
| @param maxLength The maximum length of the hostory list. The
|                  list truncates its tail when growing longer.
| @param blankDefault If true, maintains an empty string as the
|                  first (most recent) entry.
|
protected History(int maxLength, boolean blankDefault)
   {        
      this.maxLength = maxLength;
       
      history = new ArrayList<String>(maxLength+1);
      history.add("");
       
      blankAtStart = blankDefault;     
      }

   
   


| Put an entry into the history list. This method is only for
| initialisation through subclasses. It does not check for
| duplicates or maxlength.
|
protected void put(String value)
   {
      history.add(value);     
      }

   
   


| Return the history of used classes.
|
public List getHistory()
   {        
      return history;     
      }

   
   


| Add a string to the history of used strings.
|
| @param newString  the new string to add
|
public void add(String newString)
   {
      if (newString != null && (newString.length() != 0)) { 
         
         history.remove(newString);

         if (blankAtStart) {
            history.add(1, newString);             
            }
           

         else {
               
         
         if (((String)history.get(0)).length() == 0)
         history.remove(0);
         history.add(0, newString);             
         }

           
      
      if (history.size() > maxLength)
      history.remove(maxLength);         
      }     
   } 
}